The tale of Citigroup is really the tale of one man, Sandy Weill – a Brooklyn-born stockbroker who had ambitions to build the biggest banking group in the world.

Armed with little more than a relentless energy and aggressive zeal, he set out on his quest to conquer the financial markets in the early 1980s. By 2005, Citigroup's $108bn of revenues eclipsed the economies of countries such as the Czech Republic, Singapore and New Zealand, briefly becoming one of the largest 50 companies in the world. As much as any of the recent crises in the financial markets, the dismantling of Mr Weill's empire signals the end of an era.

Mr Weill began at American Express, where he hired a dynamic young graduate straight out of Harvard Business School as his personal assistant. That man was Jamie Dimon, now chief executive of JP Morgan – the bank that rescued Bear Stearns and Washington Mutual, and remains one of the few resilient Wall Street giants.

Mr Weill and Mr Dimon were not sated by AmEx and left to start their own business Primerica in the mid 1980s. At Primerica, they discovered their infamous lust for deal-making, building it into a broad ranging financial services group that ultimately became Travellers. Along the way, Mr Weill picked up an aspiring lawyer called Charles "Chuck" Prince.

For much of Mr Weill's bid to create a one-stop financial "supermarket", Mr Prince was his chief lawyer. Then, in 1998, Mr Weill pushed through the deal that created the Citigroup banking behemoth by merging Travelers with Citicorp. Citi became the biggest bank on Wall Street – a colossus employing over 325,000 people in businesses ranging from high-street banking and credit cards to investment banking and wealth management across the world.

But the scale of Mr Weill's ambition was also its undoing. Integrating such a disparate and massive operation was not his strength and the problem was never properly dealt with. Rows over strategy with Mr Dimon ensued and Mr Dimon left. Mr Dimon's departure thrust Mr Price forward as Mr Weill's successor. As a lawyer, Mr Prince never commanded the same respect on Wall Street, which began to expose the cracks in the lumbering giant.

Without room for expansion, critics said, Citigroup's strategy lacked purpose. Mr Prince's tenure since taking over in 2003 was dogged with rumour about his departure as the bank failed to capitalise on its size, but it was his reaction to the financial crisis that sealed his fate. In perhaps the most infamous words of the crisis, he explained last summer that the bank was not pulling back from the markets because "as long as the music is playing, you've got to get up and dance. We're still dancing."

Crippled by the largest exposure to sub-prime and other toxic debt, Citi has wracked up losses of $20bn in the past 12 months. Mr Prince should have sat down before the music stopped.

Citi cast its net wide for his successor, after Mr Prince left at the bank end of last year, but few wanted the job. Royal Bank of Scotland's Sir Fred Goodwin and Deutsche Bank's Josef Ackermann are said to have turned the role down. It ended up with the internal candidate Vikram Pandit, who has begun the inevitable dismantling of the empire. He has grasped the nettle, cutting 75,000 jobs in the past year and shutting down businesses that no longer have a future.

Ultimately, Citi – a massive play on growth of the financial markets – outgrew both itself and the capacity for world's banking services. A tale of overambition on the one hand, its misfortunes might also be seen as a proxy for the future of the markets.